[XeTeX] Japanese and English document

[Robert Beckett]

Hi All,
I write letters in English, but sometimes include a few words or a
paragraph in Japanese.The following is my setup. To my eye, the results seem ok, but I'm not
sure. Does anyone have any advice on how to get the best possible spacing,
etc. for both English and Japanese?

Thanks
Bob

\documentclass[12pt,oneside,a4paper]{memoir}
\usepackage{fontspec,xunicode,xltxtra}  
\usepackage{xCJK}
\XeTeXinputencoding "bytes"
\XeTeXdefaultencoding "bytes"
\setmainfont[Mapping=tex-text, Numbers=OldStyle,
BoldFont=AGaramondPro-Bold,
ItalicFont=AGaramondPro-Italic]{AGaramondPro-Regular}

\setCJKmainfont{KozMinProVI-Regular}

\begin{document}

Some English text.

\begin{CJK}{UTF8}{}

Some Japanese text.

\end{CJK}

\end{document}